This invention is directed to a control valve and more particularly to such a valve for maintaining a constant peripheral velocity and constant velocity head before and after the intended control point of the valve, and is particularly directed to "angle pattern" control valves where the direction of fluid flow entering the inlet chamber is at 90.degree. to the direction of fluid flow directly from the control orifice. Therefore, the valve of the present invention does not include what are commonly referred to as butterfly, ball, plug, gate, or needle valves. It does include angle pattern valves utilizing a sleeve with multiple nozzles, or a single annular control orifice whose peripheral length is small compared to its peripheral circumference. Valves utilizing the present invention may range in size from quite small (about one inch in diameter) to quite large (96 inches in diameter).
One of the problems associated with known valves of the general type to which the present invention relates, including valves commonly referred to as sleeve valves or multi jet sleeve valves as exemplified in U.S. Pat. No. 2,596,534, is that they must be operated with back pressure to prevent excessive vibration. When operated under high flow rates without back pressure on the valves, such as under free discharge conditions, the valves vibrate. Such vibration causes excess wear and noise. To reduce the vibration problem, it was required that the valves be operated with back pressure or a limiting velocity in the case of the angle pattern valve. In some cases, an adjustable mechanical stop was used to limit the opening stroke of the valve to reduce vibration. Therefore, with either of these solutions while vibration was reduced or eliminated, the valve's capacity was also reduced.
In accordance with the present invention, such vibration is eliminated without significantly reducing the flow capacity of the valve. The valve of the present invention need not be operated with back pressure or with mechanical stops that limit the opening of the valve reducing the valve's capacity.
Generally, the control valve of the present invention includes a valve body with first and second valve members supported by the valve body. The valve has a fluid inlet, a fluid outlet, and a fluid passage from the inlet to the outlet. The valve body has a hollow portion in the fluid passage that defines a cylindrical section. At least one of the valve members is movable relative to the other, with a control orifice defined between the two members such that the fluid flows through the orifice. The size of the orifice is changed by a movement of one of the valve members to control the amount of fluid that flows through the valve, and to open and close the valve. An inlet chamber is located in the passage at the entrance of the control orifice. The passage and control orifice direct the flow of fluid such that the fluid turns 90.degree. as it flows from the chamber into the control orifice. Moreover, the direction of fluid flow as the fluid enters the chambers is at 90.degree. to the longitudinal axis of the cylindrical section of the valve body with the fluid flowing radially inwardly through the control orifice. The cross section of the chamber taken perpendicular to the longitudinal axis of the cylindrical section of the valve body is generally an annulus, and it is of particular importance that in accordance with the invention the chamber is shaped such that the velocity of the fluid through the chamber is generally constant.
To achieve this generally constant velocity through the chamber, the cross sectional area of the chamber taken perpendicular to the direction of fluid flow within the chamber, before the fluid turns into the control orifice, diminishes in the direction of fluid flow through the chamber. In other words, the chamber becomes progressively smaller in cross section taken perpendicular to the direction of fluid flow within the chamber, the chamber becoming progressively smaller as the fluid moves through the chamber. In the valve of the present invention, this is accomplished by offsetting the control orifice from the longitudinal axis of the cylindrical section such that the annular chamber is eccentric.
The result is a control valve that maintains generally constant velocity through the chamber, does not have significant velocity head loss, will operate at very high velocities and under free discharge or negative outlet head pressure conditions, is without significant vibration, and operates at very low noise levels.
These and other objectives and advantages of the present invention are apparent from the detailed description to follow.